Marlon T. "X-Large" Moore sure looks like one of the dumbest criminals in Miami history.

Late last year, the 38-year-old Miami native was arrested while on probation from federal prison for filing false tax claims — to the tune of $14 trillion.

Yeah, trillion. With a t.

If the IRS had paid out, Moore's return would have exceeded the U.S. national debt. Instead, Moore snagged a two-year stay at the federal pen after pleading guilty to fraud.

Not too bright, right?

Au contraire, says Damien Higgerson, a convicted coke dealer who spent years in the big house with Moore, who had earned a six-year stay in 2001 after he got caught laundering money for a cocaine ring.

X-Large wasn't X-Dumb, Higgerson says. He just bought into the wacky ideas of an anti-government movement called "Sovereign Citizens" or "Redemption." The Internet-fueled fringe preaches that people can snag unlimited cash by manipulating IRS forms. To prisoners, it's an easy sell.

"This stuff is huge in prison right now, and Marlon really believed in it," says Higgerson, who was booked for 151 months for selling coke. "He wasn't trying to rob nobody."

Higgerson first met Moore in the Coleman Correctional Complex, a federal prison just north of his hometown of Orlando. He remembers him as a "soft-spoken, really nice guy."

Inside, the pair met another felon named Willie Bernard Cameron, serving a term for bank robbery. The three soon fell into a circle that preached the "Sovereign Citizen" bible.

The basic idea: When you're born, the U.S. government also creates a legal doppelganger called a "straw man" by giving you a birth certificate and Social Security Number without your consent. Therefore, believers say, the government can only control your "straw man" — not the real flesh-and-blood you. Taxes, laws, police? They don't really apply.

Sounds nutty, right? But the idea has inspired everyone from Oklahoma City bombing henchman Terry Nichols to the Montana Freeman Militia to Wesley Snipes, according to a report by the Anti-Defamation League.

To that list, Higgerson says, add poor Marlon T. Moore.

Moore walked out of Coleman in December 2007. In May 2008, he filed separate forms asking for $5.95 trillion, $2.97 trillion, and $6 trillion. He also sent the IRS a letter explaining his new belief he was a "sovereign citizen," Higgerson says.

A few weeks later, the recently paroled Willie Cameron did the same, asking for a measly $52,918.97.

Higgerson says he planned to do the same after his release but decided to wait. When the feds swooped in the next summer, arresting Moore and Cameron on fraud charges, he realized the "Sovereign Citizen" theory might not be all it's cracked up to be.

Which isn't to say Higgerson has given up on the idea.

"I really believe if you look at and study what these guys have to say, it's mostly true. But the fact is, it could never happen in practice," Higgerson says, sounding wistful. "Those guys in charge are just too damned powerful."